[Busec] BUsec next week: Huijia Rachel Lin (Monday 10AM)

Sharon Goldberg goldbe at cs.bu.edu
Fri Nov 16 15:31:17 EST 2012


We are back to our regularly scheduled seminars for the next two weeks.

This Monday 10AM, our own Rachel Lin will tell us about constant round
concurrent zero knowledge.  The following week, we will have Aggelos
Kiayias, from U Athens, visiting us and speaking at the seminar.

Lunch will be provided and abstracts are below.

See you then,

Constant-Round Concurrent Zero Knowledge From Falsifiable Assumptions
Speaker: Huijia Rachel Lin (MIT/BU)
Nov 19, 10-11:30 AM
MCS 137, 111 Cummington St, Boston MA

We present a constant-round concurrent zero-knowledge protocol for
NP. Our protocol is sound against uniform polynomial-time attackers,
and relies on the existence of families of collision-resistant
hash functions, and a new (but in our eyes, natural) falsifiable
intractability assumption: Roughly speaking, that Micali's
non-interactive CS-proofs are sound for languages in P.

Resource-based Corruptions and the Combinatorics of Hidden Diversity
Aggelos Kiayias (U. Athens & U. Connecticut)
Monday Nov 26, 10AM

Abstract. In the setting of cryptographic protocols, the corruption of a
party has traditionally been viewed as a simple, uniform and atomic
operation, where the adversary decides to get control over a party and this
party immediately gets corrupted. In this paper, motivated by the fact that
different players may require different resources to get corrupted, we put
forth the notion of resource-based corruptions, where the adversary must
invest some resources in order to corrupt them.

If the adversary has full information about the system configuration then
resource-based corruptions would provide no fundamental difference from the
standard corruption model. However, in a resource “anonymous” setting, in
the sense that such configuration is hidden from the adversary, much is to
be gained in terms of efficiency and security.

We showcase the power of such hidden diversity in the context of secure
multiparty computation (MPC) with resource-based corruptions and prove that
it can effectively be used to circumvent known impossibility results.
Specifically, if OPT is the corruption budget that violates the
completeness of MPC (the case when half or more of the players are
corrupted), we show that if hidden diversity is available, the completeness
of MPC can be made to hold against an adversary with as much as a B · OPT
budget, for any constant B > 1. This result requires a suitable choice of
parameters (in terms of number of players and their hardness to corrupt),
which we provide and further prove other tight variants of the result when
the said choice is not available. Regarding efficiency gains, we show that
hidden diversity can be used to force the corruption threshold to drop from
1/2 to 1/3, in turn allowing the use of much more efficient
(information-theoretic) MPC protocols.

Among others, the talk will go into details regarding the modeling of the
corruption process, the abstraction of the corruption game as a
combinatorial problem, and the formalization
of the properties of inversion effort preserving functions and hardness
indistinguishability that are needed to model hidden diversity in the
setting of computational corruptions.

Joint work with Juan Garay, David Johnson, Moti Yung.
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